Piezo-electric anti-countermine circuit



1 Aug, 13, 1957 w. s. MACDONALD PIEZO-ELECTRIC ANTI-COUNTERMINE CIRCUIT Filed June '7, 1945 2 Sheets-Sheet l WA. Maadanald "Aug. 13, 1957 w. s. MACDONALD I PIEZO-ELECTRIC ANTI-COUNTERMINE C IRCUIT Filed J-fine 7, ,1945 Y 2 Sheets-Sheer 2 Patented Aug. 13, 1957 PIEZO-ELECTRIC ANTI-COUNTERMINE CIRCUIT Waldron S. Macdonald, Washington, D. C.

Application June 7, 1945, Serial No. 598,189

13 Claims. (Cl. 102-18) :(Granted under Title 35, U. S. Code (1952), sec. 266) This invention relates generally to firing control mechanisms for a depth charge. More pecifically, the invention relates to an electric circuit included in the firing control system of a depth charge and in which transducer means is employed to prevent premature firing of the depth charge in response to countermine shocks received thereby.

The primary object of the present invention is to provide new and improved means for preventing the premature detonation of a depth charge in response to countermine shock received thereby.

Another object in a depth charge having a firing circuit is to prevent the operation of the firing circuit in response to countermine shocks received by the depth charge.

Another object of the invention is to cause a voltage to be generated in response to countermine shocks and to utilize the voltage thus generated in preventing the premature detonation of a depth charge in response to such shocks.

Another object in a depth charge having a signal channel for controlling the firing circuit thereof is to prevent the detonation thereof when pressure impulses received by the depth charge initiate the operation of the signal channel thereof.

Another object is the provision of new and improved means for preventing the premature detonation of a depth charge in response to countermine shocks received thereby which is rugged in construction, reliable in service and economical to manufacture.

Additional objects and advantages will become more clearly apparent as the description proceeds, reference being made tothe accompanying drawings of which:

Fig. 1 illustrates in diagrammatic. form a complete firing control system for a depth charge including the circuit of the instant invention in accordance with the preferred embodiment thereof; and,

Fig. 2 illustrates in diagrammatic form another complete firing control system for a depth charge including the circuit of the instant invention.

A detailed description of the present invention and the operation thereof will now be given with reference to Fig. l of the drawings. The depth charge firing control system of Fig. 1 comprises a signal channel which utilizes the difference in intensity at different points in the magnetic field of a submarine detected by a pair of opposedly connected and balanced pickup coils and 11 arranged in predetermined spaced relation with respect to each other to control a signal amplifying mechanism indicated generally by the numeral 12, thereby to operate an electron discharge device 13 connected to the output of the amplifying mechanism 12 and fire a detonator 14 through a firing relay 15 when the difference in the magnetic signals received by each of the coils 10 and 11 has reached a predetermined value. The signal channel of the firing control system shown in Fig. 1 is described and claimed in the copending application of W. S. Macdonald et al. for Firing Control Mechanism for a Depth Charge, Serial No. 453,550, filedAugust 4, 1942, and for a more detailed description thereof, reference is made to said application.

The electric circuit of the present invention comprises a transducer 16, preferably of the piezo-elect1ic crystal type, operatively connected to a condenser 17. The crystel 16 is arranged within the depth charge in any suitable manner but preferably is mounted on the plate which supports the elements comprising the firing control system, in which case the crystal is shocked through the supporting plate. The crystal 16, moreover, is adapted to peak at substantially 10,000 cycles per second in order to reduce to a minimum any delay in the generation of voltage by the crystal. A suitable electric valve device 18 preferably of the trigger type is included in the circuit and comprises a plate 19, a cathode 21, a control grid 22 and a suppressor grid 23, the suppressor grid being tied to the cathode. Static operating potentials are applied to the plate 19 and control grid 22 of the trigger tube 18 respectively by battery BA through resistor R3 and by battery BA1 through resistor R4, respectively, the cathode 21 receiving its potential from battery BA2 through resistor R5. The firing relay 15, it will be noted, is common to the plate circuits of each of the tubes 13 and 18.

The operation of the signal channel of the firing control system of Fig. 1 will now briefly be described. As a depth charge employing this system descends through a body of water, the hydrostatic device 26 is operated in a well known manner to supply static operating potentials to the various elements of each of the tubes in the system. As the depth charge travels downward into suflicient close proximity with respect to a submarine, the magnetic signal received by the coils 10 and 11 increases until the depth charge has reached a position adjacent the submarine at which time the signal is of sufiicie-nt strength to cause the tube 13 to fire. When this occurs, the normally charged condenser 27 discharges through resistor R2 and through the firing relay 15. The condenser 27 is of sufficient capacity and the resistor R2 of sufficient resistance to cause a flow of current as condenser 27 discharges of sufiicient strength and duration to operate relay 15. As armature 28 of relay 15 moves into engagement with contact 20 thereof, potential is applied to the electroresponsive detonator 14 from battery BA1 thereby operating the detonator and exploding the depth charge. The foregoing operation is described in greater detail in the aforesaid application of W. S. Macdonald and reference is made thereto.

The operation of the system, including the circuit of the present invention, in response to a wave of hydrostatic pressure such, for example, as may be received by the depth charge as the result of an explosion of another depth charge or similar explosion within the vicinity thereof will now be described.

When such an explosion occurs, the wave of hydrostatic pressure resulting therefrom strikes the depth charge, thereby stressing the crystal 16 and causing an electromotive force to be generated thereby. The condenser 17 is connected to the control grid 22 of tube 18 and is adapted to be charged by the voltage generated by the crystal and as the charge on condenser 17 builds up, the voltage on the control grid 22 of tube 18 also builds up in a positive direction. When the control grid breakdown voltage of tube 18 is reached, the tube is caused to conduct in a well known manner. When this occurs, the normally charged condenser 27 discharges through resistor R1 and the tube 18, thereby abruptly reducing the potential applied to the plate 10 thereof and extinguishing the tube when the plate potential is reduced below the discharge sustaining potential thereof.

As condenser 27 discharges, the plate potential of tube 13 in the signal channel is also decreased thereby renden ing tubenl ineffective to operate relay 15 until conover a .longerperiod .of time thanresistor R1 receives from the crystal controlled tube 18 when tube 18 fires. Therefore in the event'that a countermine signal causes both of thetubes l3 and ,18Jtofirexsimultaneously, condenser :27 discharges'throughresistor Rland relay 15 remains-unoper-ated.

"Fig. 2'of. the drawingsshows in diagrammatic form .another firing control system for adepth'chargepthe system being similar to that shown in Fig. .1 with the exception that'thefiring relay. 15 thereof is replaced by an electron discharge device 32.of the same type as tube 13. .In. order .to retain the delay which was provided by the relatively slow make action of the relay contacts 28 and $29, a. condenser 33 is arranged in the plate circuit of tube 13. and another condenser34 is connected to the. controlv grid 35 of tube 32. When tube 13 is caused to fire,'zcondenser 33 discharges through tube 13 and a resistor R6 thereby drivingthe potential applied to the control' grid..35. of. tube 32 to a value below ground potential. As condenser" 33 discharges, the plate potential on tube 13. is ,decreasednntil it falls below the main gap sustaining voltage thereof, whereupon tube 13 is extinguished and condenser .33 is recharged by battery BA through resistor R3 .andresistor R7 and the plate potential of the'tube 13is increased to the proper static operating value.

.During the recharge of condenser 33, the condenser 34 receives a positive charge and the voltage .applied to the control grid of;tube .32 is.elevated to a value corresponding to the control gap breakdown voltage of the tubelwhereby'the tube will be fired when such voltage is reached.

through the detonator sufficiently to prevent the opera tion thereof. It will be understood, of course, that the plate potentials of the tubes 13 and 32 are decreased as condenser'27 discharges thus rendering these tubes ineffective-until condenser 27 is again charged. It should be pointed out here that as condenser 27 is recharged, the signal channel may be operated to fire tube 32 and explode the depth charge provided a magnetic signal of sulficient strength'is detected by the coils and 11 whereby the operation of the anti-countermine circuit will not cause the depth charge to become a dud if the charge passes sufli'cientlyclose to a submarine.

It should now be apparent that an anti-countermine circuit for a depth charge has been provided which is well adapted'to fulfill the aforesaid objects of the invention.

While the invention has been described with particularity in reference to an example thereof which gives satisfactory results, it readilywill be apparent to those skilled in the art, .after understanding the invention, that further embodiments, modifications and changes may be made without departing from the spirit and scope thereof as defined by the claims appended heretoa l The present invention may be manufactured and used by or for the Government of the United States of America for governmental purposes without payment of any royalties thereon or therefor. V a

What is claimed as new and. desired to be secured by Letters Patent of the United States is:

' 1. In afiring :control'systemfor a .depth.charge,l.the combinationcf means for firing said .depth charge in response to changes'in the magnetic field within the vicinity thereof, a normally charged condenser included'in said firing means, means including an electron discharge device for discharging said condenser and-rendering said firing means .are actuated simultaneously thereby to prevent,

means ineffective for 'a'predetermined interval when the device operates, and a voltage generating transducer dis- V posed within the depth charge for'operating said electron discharge device in response to the voltage. generatedby the transducer as countermine-shocks arerreceived by said depth charge. i

2. In a firing control system for a depth charge, the

generated by thetransducer'for discharging the condenser through said resistor when said firing and said' disabling firing of said depth charge. 3. In a firing control system for a-depth charge,'the combinationof means for firing said depth charge in response tochanges in the magnetic field adjacent thereto; protective means including a voltage generating transducer for rendering said firing means inefliective for a predetermined interval when pressure impulses are received by said depth charge, a circuit including a resistor operatively connected to said protective means, a normally charged condenser disposed in said circuit and arranged to be discharged through said resistor, and means'controlled v by thevoltage generated by the transducer for discharging the condenser through the resistor when said firing and said protective means are actuated simultaneously thereby to prevent firing of said depth charge.

' 4. In a firing control system fora'depth charge, the combination of means for firing said depth charge in response to changes in' the magnetic field adjacent thereto, a normally charged condenser included in said firing means, an electron discharge device for discharging said condenser'and disabling said firing means as the device operates, a voltage generating transducer foroperating said electron discharge device in response to the voltage generated by the transducer as countermine shocks are received by said depth charge, and circuit means including a resistor connected to the discharge path of the condenser for preventing the firing of said depth charge when said firing means and said electron discharge device are operated simultaneously.

combination of means for firing said depth charge in re sponse to changes in the magnetic field adjacent thereto; means including an electron discharge device for rendering said firing means ineffective for a predetermined in terval when the device operates, a voltage generating transducer disposed Within the depth charge for operating said electron discharge device in response to countermine shocks received by said depth charge, a circuit including said discharge device, a resistor in said circuit, and a normally charged condenser in .said circuit andarranged to be discharged through said resistor and said discharge device when said firing means and said-elecw tron discharge device are operated simultaneously thereylo preventfi ns otsaid p h c 6. In a firing control system for a depth charge, the combination of a circuit for firing said depth charge, means for detecting changes in the magnetic field adjacent said depth charge and for operating said firing circuit in response to magnetic field changes of predetermined character, a trigger type electron discharge tube having a control grid and adapted to be fired in response to a potential of predetermined value applied to the control grid thereof, a normally charged condenser in said firing circuit, said trigger tube being arranged to discharge said condenser and render said firing circuit ineffective for a predetermined interval when the trigger tube is fired, and a voltage generating transducer for applying said predetermined value of potential to said trigger tube in response to countermine shocks received by said depth charge.

7. In a firing control system for a depth charge, the combination of a signal channel for receiving magnetic signals and for generating electrical signals in accordance therewith, a firing circuit, a circuit-closing device controlled by said electric-al signals and adapted to close said firing circuit when the electrical signals are of predetermined character, and means including a crystal device for preventing the operation of said circuit-closing device when pressure impulses are received by said depth charge.

8. In a firing control system for a depth charge, a firing circuit, means for controlling the operation of said firing circuit, a signal channel including a magnetic responsive device for initiating the operation of said circuit controlling means when magnetic signals of predetermined character are received by the magnetic responsive device, a normally charged condenser operatively connected to said controlling means and arranged to discharge therethrough in response to operation thereof, an electron discharge device for causing the condenser to be discharged therethrough to prevent operation of said circuit controlling means when the electron discharge device is operated, and a voltage generating device in electrical connection with said electron discharge device for initiating the operation thereof in response to the voltage generated by the voltage generating device when pressure impulses are transmitted through the surrounding water.

9. In a firing control system of the character disclosed, a normally charged condenser, a plurality of discharge paths for said condenser, a firing circuit, an electroresponsive device included in one of said discharge paths for controlling the operation of said firing circuit, a signal channel including means for detecting changes in a magnetic field and for generating electrical signals in accordance therewith, an electron discharge device included in said signal channel and arranged in said one of said plurality of discharge paths for causing said condenser to discharge through said electroresponsive device when said electrical signals are of predetermined character, a second electron discharge device arranged in another of said plurality of discharge paths for causing said condenser to discharge therethrough when the second electron discharge device is operated, and means including a crystal device for initiating the operation of said second electron discharge device when pressure impulses are received by the crystal device.

10. In a firing control system of the character disclosed, a normally charged condenser, a plurality of discharge paths for said condenser, a firing circuit, an electroresponsive device included in one of said discharge paths for controlling the operation of said firing circuit, a sig nal channel including means for detecting changes in a magnetic field and for generating electrical signals in accordance therewith, an electron discharge device included in said signal channel and arranged in said one of said plurality of discharge paths for causing said condenser to discharge through said electroresponsive device when said electrical signals are of predetermined character, a second electron discharge device arranged in another of said plurality of discharge paths for causing said condenser to discharge therethrough when the second electron discharge device is operated, means including a crystal device for initiating the operation of said second electron discharge device when pressure impulses are received by the crystal device, and circuit means for causing said condenser to discharge through said other of said plurality of discharge paths when said first and second electron discharge devices are operated simultaneously.

11. In a firing control system of the character disclosed, a source of electrical energy, a firing circuit, an electroresponsive device for initiating the operation of said firing circuit as the device operates, means responsive to changes in a magnetic field and adapted to cause electrical energy to flow from said source of energy through said electroresponsive device when the magnetic field changes are of predetermined character, a trigger type electron discharge tube having a control grid and adapted to cause electrical energy to flow from said source of energy through the tube when a potential of predetermined value is applied to the control grid thereof, and circuit means including a voltage generating transducer for generating and applying said predetermined Value of potential to said trigger tube in response to pressure impulses received by said system.

12. In a firing control system of the character disclosed, a source of electrical energy, a firing circuit, an electroresponsive device for initiating the operation of said firing circuit as the device operates, means responsive to changes in a magnetic field and adapted to cause electricl energy to flow from said source of energy through :said electroresponsive device when the magnetic field changes are of predetermined character, a trigger type electron discharge tube having a control grid and adapted to cause electrical energy to flow from said source of energy through the tube when a potential of predetermined value is applied to the control grid thereof, a voltage generating transducer for generating and applying said predetermined value of potential to said trigger tube in response to pressure impulses received by said system, and circuit means for causing electrical energy to flow through said trigger tube when pressure impulses and magnetic field changes of said predetermined character are received by said system simultaneously.

13. In a firing control system for a depth charge, the combination of means for firing said depth charge in response to changes in the magnetic field within the vicinity thereof, a normally charged condenser included in said firing means, means for discharging said condenser and rendering said firing means inefiective for a predetermined interval when the discharge means operates, and means operated to generate a voltage in response to countermine shocks for operating said discharge means.

References Qited in the file of this patent UNITED STATES PATENTS 1,310,568 Heap et al. July 22, 1919 1,448,976 Palmer Mar. 20, 1923 2,361,177 Chilowsky Oct. 24, 1944 2,400,549 Glennon et a1. May 21, 1946 

